Question about wastegate popping

[123lilc]

so i'm dealing with a boost holding problem, i cannot get the car to hold more that about 15psi of boost. it will shoot up to around 26ish and then quickly drop to about 15.
is this the internal wastegate popping open? i believe the WG spring is 12-14psi (GT28R)
I unplugged the line from the WG and i would not go past 15PSI

[MoparFreak69]

Make sure your diverter valve is functioning correctly. I had one that would blow open at about 16PSI. Also double check for any boost leaks. A slightly loose clamp can hold lower pressures but allow greater pressure to escape past it. If all that is good it may be time to pull the turbo and physically inspect the wastegate flapper for damage/breakage/cracks.

[NOBR8KSS]

Another vote for the diverter valve

[customa4]

OP, don't you already have another thread running on almost the same exact topic? Post in the same thread to keep everyone informed on what has been tested so far. Starting new threads means the diagnosis has to start from scratch again.

http://www.audizine.com/forum/showth...2#post11529282

You're gonna have to get your hands dirty. Reading the first thread, it looks like you're waiting for the answer to fall out of the sky. We can help you but you gotta dive in and start testing things. Do you have access to VCDS? Logs will help you out with this problem. Since you have the Forge 007 DV, make sure you have the proper spring in there. Find out what color it is. Different colored springs are for different levels of boost. If you have a spring that is too weak that could be a reason why you're not holding boost. I bought a kit some time back for the 007 and have a few different springs if I could find them. I'd be more than happy to send one your way if you could figure out which color you have and which one you need.

[123lilc]

OP, don't you already have another thread running on almost the same exact topic? Post in the same thread to keep everyone informed on what has been tested so far. Starting new threads means the diagnosis has to start from scratch again.

http://www.audizine.com/forum/showth...2#post11529282

You're gonna have to get your hands dirty. Reading the first thread, it looks like you're waiting for the answer to fall out of the sky. We can help you but you gotta dive in and start testing things. Do you have access to VCDS? Logs will help you out with this problem. Since you have the Forge 007 DV, make sure you have the proper spring in there. Find out what color it is. Different colored springs are for different levels of boost. If you have a spring that is too weak that could be a reason why you're not holding boost. I bought a kit some time back for the 007 and have a few different springs if I could find them. I'd be more than happy to send one your way if you could figure out which color you have and which one you need.

My bad
I don't believe that the DV is the problem, because i have put a lot of washer in it to act as shims and then reversed the DV and got no change. So i believe i have ruled that one out.
i do have VCDS! i have logged requested boost vs actual boost and found out that my actually boost is higher than requested boost so im at a total loss

[123lilc]

Bump/

[customa4]

Can you post the logs that you made?

[123lilc]

this is second gear full throttle, i did not let off the gas once and for some reason boost drops off so fast and continues dropping off. it peaks at 28 holds for a second then drops really quickly to 19 then slowly goes down and holds either 15 or 10 (it changes) keep i mind this is in second gear and under full throttle



Friday 8 April 2016 18:27:46:60755-VCID:336520D451D83BA6B3-5140 VCDS Version: Release 15.7.4 (x64) Data version: 20160216
8E0 909 518 F 1.8L R4/5VT G01 0001

Group A: '020 Group B: '001 Group C: '115
Timing Retardation Timing Retardation Timing Retardation Timing Retardation Engine Speed Coolant Lambda Control Basic Setting Engine Speed Engine Load Boost Pressure Boost Pressure
TIME Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4 TIME (G28) Temperature (G62) Bank 1 Requirements TIME (G28) (specified) (actual)
Marker STAMP °KW °KW °KW °KW STAMP /min °C % STAMP /min % mbar mbar
0.01 0 0 0 0 0.09 2000 96 -7.8 1101001 0.26 2000 27.1 970 990
0.43 0 0 0 0 0.61 2000 96 -0.8 1101001 0.78 2000 27.1 970 990
0.94 0 0 0 0 1.11 1960 96 -0.8 1101011 1.28 2000 27.1 970 990
1.45 0 0 0 0 1.62 1960 96 0 1101011 1.79 2000 26.3 970 990
1.95 0 0 0 0 2.12 2000 96 0 1100001 2.3 2040 78.2 1880 1000
2.47 0 0 0 0 2.64 2120 96 0 1100001 2.81 2160 85.7 1880 1080
2.97 0 0 0 0 3.14 2200 96 -3.9 1101001 3.31 2240 93.2 1890 1150
3.48 0 0 0 0 3.64 2320 96 -2.3 1101001 3.81 2360 100 1880 1220
3.99 0 0 0 0 4.16 2480 96 0.8 1101001 4.32 2480 103.8 1880 1270
4.49 0 0 0 0 4.66 2600 96 3.9 1101001 4.83 2640 108.3 1880 1330
4.99 0 0 0 0 5.16 2720 96 6.3 1101001 5.33 2800 115 1890 1400
5.49 0 0 0 0 5.66 2880 96 8.6 1101001 5.84 2960 124.8 1900 1490
6 0 0 0 0 6.17 3040 96 7 1101001 6.34 3120 134.6 1940 1590
6.51 0 0 0 0 6.68 3240 96 7.8 1101001 6.85 3320 148.9 2000 1720
7.02 0 0 0 0 7.19 3480 96 8.6 1101001 7.36 3520 166.9 2130 1910
7.52 0 0 0 0 7.7 3680 96 11.7 1101001 7.86 3760 191.7 2210 2140
8.03 0 0 0 0 8.2 3960 97 18 1101001 8.37 4080 191.7 2240 2470
8.54 0 0 0 3 8.7 4280 97 25 1101001 8.87 4400 191.7 2230 2540
9.04 3 0 3 4.5 9.21 4600 96 25 1101001 9.38 4680 191.7 2220 2470
9.54 3 0 3 4.5 9.71 4880 97 25 1101001 9.88 4960 191.7 2220 2440
10.05 3 0 3 4.5 10.21 5160 96 25 1101001 10.38 5240 191.7 2180 2450
10.55 3 0 3 4.5 10.72 5440 96 25 1101001 10.89 5520 191.7 2150 2420
11.05 3 0 3 4.5 11.23 5680 96 25 1101001 11.4 5760 191.7 2170 2450
11.57 3 0 3 4.5 11.73 5920 96 25 1100001 11.9 6000 191.7 2180 2350
12.06 3 0 3 3.8 12.23 6080 96 14.8 1100001 12.4 6160 157.1 2180 1830
12.57 3 0 3 3.8 12.74 6240 96 14.8 1100001 12.92 6280 153.4 2190 1790
13.08 3 0 3 3.8 13.25 6360 95 14.8 1100001 13.41 6400 146.6 2200 1720
13.58 3 0 2.3 3.8 13.75 6480 95 13.3 1100001 13.92 6520 140.6 2200 1660
14.09 2.3 0 1.5 3.8 14.25 6600 95 11.7 1100001 14.41 6640 139.1 2180 1650
14.59 2.3 0 1.5 3.8 14.76 6720 95 10.2 1100001 14.93 6760 139.1 2180 1660
15.1 1.5 0 0.8 3.8 15.27 6840 95 7.8 1101001 15.43 6840 132.3 2170 1580
15.6 1.5 0 0.8 3.8 15.76 6920 94 6.3 1101001 15.93 6920 130.1 2080 1560
16.1 1.5 0 0.8 3.8 16.28 6760 94 0 1110001 16.45 6560 12.8 970 1570
16.61 0 0 0 0 16.78 6040 94 0 1110001 16.95 5800 15 970 1170
17.12 0 0 0 0 17.28 5360 94 0 1110001 17.45 5120 13.5 970 1070
17.62 0 0 0 0 17.78 4680 93 0 1110001 17.95 4480 13.5 970 1040
18.13 0 0 0 0 18.31 4040 93 0 1110001 18.48 3840 14.3 970 1020
18.64 0 0 0 0 18.8 3480 93 0 1110001 18.97 3280 15 970 1010
19.14 0 0 0 0 19.32 3000 93 0 1110001 19.49 2840 14.3 970 1000
19.66 0 0 0 0 19.83 2600 93 0 1110101 20 2440 14.3 970 1000

[123lilc]

Anyone?

[diagnosticator]

Be careful with that 26 psig boost spike! That can grenade your engine! Especially if running the stock AMB rods and pistons.

[123lilc]

Be careful with that 26 psig boost spike! That can grenade your engine! Especially if running the stock AMB rods and pistons.

oh, yikes i don't want to do that! my goal is to hold 25psi all the way to redline. is that possible with the stock rods and everything or should i shoot for holding 20psi to be safe?

[MetalMan]

I think your issue is related to your tune... the stock MAP sensor cannot read beyond ~22 psi. So I'm gonna guess that your ECU detects overboost, and then is dropping your car to soft limp mode. When in soft limp mode, the N75 is basically disabled and your boost level is limited roughly to wastegate pressure.

Was the Revo Stage 3+ tune designed for the GTX2863R? If not, it's possible this turbo isn't playing too nicely with the tune.

On a GTX2863R, I'm gonna guess 25psi is too much for the stock rods depending on how rapidly boost/torque comes on (which is determined by the tune).
For example, Motoza limited my boost with FrankenTurbo to ~20-21 psi on E85 while I was on stock rods... this is a lesser turbo than you have despite me running E85.

[123lilc]

I think your issue is related to your tune... the stock MAP sensor cannot read beyond ~22 psi. So I'm gonna guess that your ECU detects overboost, and then is dropping your car to soft limp mode. When in soft limp mode, the N75 is basically disabled and your boost level is limited roughly to wastegate pressure.

Was the Revo Stage 3+ tune designed for the GTX2863R? If not, it's possible this turbo isn't playing too nicely with the tune.

On a GTX2863R, I'm gonna guess 25psi is too much for the stock rods depending on how rapidly boost/torque comes on (which is determined by the tune).
For example, Motoza limited my boost with FrankenTurbo to ~20-21 psi on E85 while I was on stock rods... this is a lesser turbo than you have despite me running E85.

The tune and the turbo go together fine, its the required hardware for stage 3. I also ran a manual boost controler and just left the N75 plugged in and the same exact thing occurred. so i don't think it would be the N75.

So i have ruled out that the DV is not the problem and the N75 is not the problem then that leaves me with either the wastegate being stuck open or the wastegate being forced open due to extreme pressure build up in the manifold. Right???

[old guy]

Question for ya. Are you running the N249 boost regulation valve?

Here's why I am asking. Looking at your log your actual boost starts to exceed your requested boost around 4,000 rpm. At that point your requested boost starts to reduce but your actual continues to climb. Then around 6,000 rpm your actual immediately drops off. One of the functions of the N249 is to protect the engine from an overboost condition. If the ECM "sees" a continued overshoot of actual vs requested boost it applies a vacuum signal to the N249 valve so it can immediately dump some of the excessive boost pressure.

[123lilc]

Question for ya. Are you running the N249 boost regulation valve?

erm so what exactly does this valve do? i have never heard of this valve. im not sure if i have this valve because i did the vac. delete. also if i were to have this valve where would it be located?

[customa4]

It's bolted to the underside of the intake manifold. Click





Not sure if you could tell by the diagram but one hose runs from the top of the DV to the left side of the N249. The other hose runs from the front of the intake manifold to the right side of the N249.

[123lilc]

oh gotcha! and i do not have that, or at lest its not plugged in i just have my DV hose going straight to the manifold, so thats not the problem

So does anyone else have any ideas im at a total loss

[123lilc]

Anyone?

[FromS60toB61.8t]

i had a similar problem on my GTX28 base file. I would hold 20-21 psi and as soon as i hit 5k rpm it would just keep climbing to around 31-32. As soon as i got my 1st revision it was fixed. Holds at 20-21 now with no hardware changes. Something about the MAP sensor and calibrating the correct BAR or something.

[old guy]

Watching your video and looking at your logs it’s apparent that something mechanical is dumping your boost all at once. So logically that seems to point to either the wastegate or DV since those are the only two things capable of repeatedly dumping that amount of boost in that time frame.

You mentioned that you replaced the N75 with a MBC and got the same thing. How did you set up and adjust your MBC? If it was set properly at 20 psi it should regulate your boost accordingly. The only way it wouldn’t do that would be if the wastegate was sticking or leaking.

Have you tried actuating the wastegate with an air nozzle and air pressure regulator? Pressurize the wastegate through the N75 hose connection and slowly turn up the pressure. Listen for any air leaks from the wastegate. If you can get your fingers to the wastegate actuator arm you can feel for when it starts to move. That will help confirm your wastegate cracking pressure. Does it move freely or does it seem to bang open all at once?

If that checks out OK then use the same air nozzle and air pressure regulator to preset the MBC and then put it back on and see how it performs.

Question for From S60toB61.8T: Are you running the N75 or a MBC?

[123lilc]

Watching your video and looking at your logs it’s apparent that something mechanical is dumping your boost all at once. So logically that seems to point to either the wastegate or DV since those are the only two things capable of repeatedly dumping that amount of boost in that time frame.

You mentioned that you replaced the N75 with a MBC and got the same thing. How did you set up and adjust your MBC? If it was set properly at 20 psi it should regulate your boost accordingly. The only way it wouldn’t do that would be if the wastegate was sticking or leaking.

Have you tried actuating the wastegate with an air nozzle and air pressure regulator? Pressurize the wastegate through the N75 hose connection and slowly turn up the pressure. Listen for any air leaks from the wastegate. If you can get your fingers to the wastegate actuator arm you can feel for when it starts to move. That will help confirm your wastegate cracking pressure. Does it move freely or does it seem to bang open all at once?

If that checks out OK then use the same air nozzle and air pressure regulator to preset the MBC and then put it back on and see how it performs.

Question for From S60toB61.8T: Are you running the N75 or a MBC?

Thanks OG! Will check that out tonight

[walky_talky20]

Pretty sure these DBW cars will also close the throttle body to keep the boost in check. I've driven an A4 1.8T in this mode before. The N75 was physically broken such that no pressure could get to the wastegate actuator. The wastegate would never open. The car was stock and drove surprisingly well, however it was pretty slow as it couldn't open the throttle very far without overboost. Data Logging the actual throttle plate angle showed what it was doing.

Now with modified ECU software, this type of safety thing could be disabled (or much more crude) as the limits are all messed with.

[old guy]

Excellent point Keith! And it's certainly easy enough to check.

[CGramme]

I think "old guy" is right on his diagnosis. You need to test the functionality of the wg. The first thing I would do is bypass the n75 and mbc. Run wg pressure and see what happens. it should fix your problem, if not then you need to take the turbo out and further inspect your wg. When you mess with the mbc can you turn it down so it doesn't spike so much? I know you know better but make sure the mbc is properly connected also.

edit- The popping may not be the wg but a backfire situation from lack of fuel flow at high boost.
Did you say you unplugged the line from the wg? That could cause very bad spikes if not worse damage. Connect the vacuum/boost line directly to your wg and see what happens. If your wg is ever not connected to a vac/boost line it will do things like what you are experiencing. An n75 or mbc simply delays a boost pressure signal to the wg until desired boost is reached.

[FromS60toB61.8t]

Watching your video and looking at your logs it’s apparent that something mechanical is dumping your boost all at once. So logically that seems to point to either the wastegate or DV since those are the only two things capable of repeatedly dumping that amount of boost in that time frame.

You mentioned that you replaced the N75 with a MBC and got the same thing. How did you set up and adjust your MBC? If it was set properly at 20 psi it should regulate your boost accordingly. The only way it wouldn’t do that would be if the wastegate was sticking or leaking.

Have you tried actuating the wastegate with an air nozzle and air pressure regulator? Pressurize the wastegate through the N75 hose connection and slowly turn up the pressure. Listen for any air leaks from the wastegate. If you can get your fingers to the wastegate actuator arm you can feel for when it starts to move. That will help confirm your wastegate cracking pressure. Does it move freely or does it seem to bang open all at once?

If that checks out OK then use the same air nozzle and air pressure regulator to preset the MBC and then put it back on and see how it performs.

Question for From S60toB61.8T: Are you running the N75 or a MBC?

Im only running an N75

[old guy]

Im only running an N75

OK. That makes sense. With the N75 the ECM has control over the boost regulation. It may not be the correct regulation (as in your case from a program issue) but it nevertheless still has control.

with an MBC the control is strictly mechanical from the MBC setting. Which is why I was questioning how 123lilc had set his MBC. It doesn't make sense that a MBC set to 20 psi would allow the turbo to continue boost unless either the MBC wasn't set to 20 psi or else the wastegate is defective.

[MetalMan]

Which is why I was questioning how 123lilc had set his MBC. It doesn't make sense that a MBC set to 20 psi would allow the turbo to continue boost unless either the MBC wasn't set to 20 psi or else the wastegate is defective.

Or there is a tear in one of the wastegate lines.

[old guy]

Or there is a tear in one of the wastegate lines.

Good point!